Purification of porous material.



I To all whom it my concern:

, No. 923,745. Original application medianuary 17, 1906, eam. 296,570. Divided and this application filed zannlar so, 190a.

UNITED STATES PATENT cr mes.

wiLLIs R. WHITNEY, or ALPLA Us, NEW YORK, AssIGNoR TO GENERAL ELECTRIC COMPANY,

4 A CORPORATION or NEW YORK;

' .runmro'e'rron on'ronous MATERIAL.

Specification of Letters Patent.

Patented June'l, 1909.

Serial No. 475,275.

Be it known that I, WILLrs-R. WHITNEY, a

' citizen of the United States, residing at Alplaus, county of Schenectady, town of Glenville, and State of New York, have invented certain new and useful Improvements inPurification of Porous Materials, (division of my'application Serial No. 296,570, filed Jan-1 uary 17, 1906 specificatlon.

My present invention relates to a rocess of which the following is a of removing impurities such as sa ts and their solutions-from orous material, by subjet-ting the material to the influence" of an electric current while suspended in a suitable solvent. In addition to this electrical treatment I use as the solvent, one-which is substantially isotonic with respect to the salt or other impurity to be removed but which'ls' 7 itself inert and harmless with respect to the porous material to be purified.

My invention is readily applicable to the purification of any porous material contaim' mg a salt or compound which will go into solution, but as showing a. specific embodimerit of my improved process I have hereinafter described it as applied to the manufacture of the insulating compound conin'mnly known in the electrical arts as fiber.

"This material is somewhat similar to hard rubber in its electrical and mechanical properties, and is used for a great variety of purposes inthe electrical arts.

in the manufacturefof fiber itiscustoumry to treat sheets of'c'ellulosebya'ssingthem through a strong solution ofch orid of zinc, after which the sheets are piled one on another and compressed into a homogeneous mass. The zinc chlorid is then removed by washing. This Washing is usually performed in several distinct steps by sus ending the porous mass in different zinc c lorid solutions of diminishing concentration until pure water is reached, for it has been found that if the material is placed directly in pure water the osmotic pressure of the salt in the pores of the mass will draw-in an excessof water-and form water blisters. These blisters cause splits in thefinal product and are the cause of great losses in material even when extreme care is take to lrevent their formation hygradual, rat nor is n by rapid washing. 'lhethicker the sheet to 0 pro- -ducediathe'greatei* the difficulty due to demotic pressure, and consequently, the greater the time and care'necessary to remove the zinc chlorid, the complete removal ofwhich is imperative. On this account, siX weeks of, washing by gradual treatment with mom and more dilute solutions ofthe chlorid is necessary for sheets of an inch or more in thickness,-thus greatly increasing thecost of material when made in thick masses.

, The osmotic pressure of a. solution depends -on its OOHCGDUEUOIL The rate of difiusion'of a salt from a concentrated solution to a dilute solution depends on the concentration differences of the two solutions with respect to that particular salt alone, and not with respect to other soluble substanceswhich may be carried in one or the other solvents.v Thesefactors I make use of in 'my improved process by utilizing, as a solvent for the zinc chlorid, a solution which is isotonic with respect. to the zinc chlorid solution to be removed. By isotonic I mean a solution having such a concentration that it will have the same osmotic pres- 'sure as the zinc chlorid solution to be removed. Thus, for example, a solution of glycerin or glucose in water may be used to wash the fibermass and thereby. remove the zinc chlorid previously employed in the chemical preparation of the mass. In this way the concentration of zinc chlorid in the wash'water is kept low and consequently its rate of diffusion from the mass into the;

Wash water is very high. The osmotic pressure of the washing solution being high, and oany desired predetermined value, does not allow the formation of water blisters in the fiber. The solution of glycerin or glucose in water used as wash .water is not in any" way detrimental to the'product. Although,

I have described this phase of my process as applied to the manufacture of fiber it will be understood that it is not limited to such use, but is a plicable to a great variety of work and invo ves broadly the use of solutlons ol harmless material to drive out an approximately isotonic solution from the interstices of porous material..

As heretofore stated, I contemplate the use of an electric current to'inm'ease"tl1e ve locity ol' motimrol the ions of the salt or impurity, such' as the zinc and chlorin ions composing-tho zinc ('lllnl'ltlevltlllll the'porone material. The apparatus for carrying electrodes.

out this feature of my improved process may be very simple consisting principally of a source 01' current and suitable electrodes placed in the glucose or other Washing liquid, and so arranged that the fiber in a sheet, or in any convenient form, can be passed through the washing liquid between the The current causes the motion of zinc to the cathode and of chlorin to the anode and these two rated atthe electrodes. By a' suitable ad- 6 dition of alkali and acid in dilute form to practically amounts .the zinc and chlorin components of water which form. an elec itrochemical point ions, g c

r What Lolaimias newand desire to' secure Letters'Patentof the United States,'is:

electrodes. and

neutralize the products liberated"at the to preserve the isotonic con: vwash ing liquid the process to the replacement of within the fiber by the dition of the of View" are H and OH elements are thus s'epal 1. The process of removing an ionized impurity from a porous material, which con- "(318138 in subjecting saidv impurity to the electrolyzing' action of an electric current, and

carrying ofi the impurity in a solvent.

2 The process of removing an inorganic salt from consists in suspending said cellulose in a suitable solvent and passing an electric current through said solvent.

' 3. The from cellu ose, which consists in washing said cellulose, and simultaneously passing a current through said solution to accelerate the removal of said zinc chlorid.

In Witness whereof, I have hereunto set my-hand this 27th day of January, 1909.

WILLIS R. WHl'lNE Y.

Witnesses:

"BENJAMIN B. HULL,

.HELEN ORFORD.

a porous mass of cellulose, which 

